Mobile communications units, such as cell phones, pagers, personal communication service (PCS) units and the like, have become common in modern society, allowing users to send and receive calls, faxes, pages, messages, etc. to or from practically any location in the United States and throughout much of the world. Such mobile devices are operated for wireless communication according to various standards with respect to modulation techniques, for example, Advanced Mobile Phone Service (AMPS) for analog technology, and Code Division Multiple Access (CDMA) or Time Division Multiple Access (TDMA) for digital technology, in order to provide communications services including calls, messages, or exchange of data or information, whether analog or digital, wherein such communications can be transmitted to or received from a wireless unit, whether a stand-alone unit or integrated within a larger system.
Mobile units communicate with system components, such as transceivers associated with system base stations, at various radio frequencies according to a given standard, where the popular combinations of frequency and standard (e.g., modulation scheme) are referred to as bandclasses. Many different bandclasses have been defined, with certain mobile communications units being capable of communicating on (i.e., supporting) several different bandclasses. Examples of such bandclasses include CDMA 800 MHz channel (Band Class 0), AMPS 800 MHz channel, NAMPS 800 MHz channel, CDMA 1900 MHz channel (Band Class 1), TACS channel (Band Class 2), JTACS channel (Band Class 3), Korean PCS channel (Band Class 4), 450 MHz channel (Band Class 5), 2 GHz channel (Band Class 6), 700 MHz channel (Band Class 7), 1800 MHz channel (Band Class 8), 900 MHz channel (Band Class 9), and a secondary 800 MHz channel (Band Class 10). More bandclasses are being defined all the time, and capability of mobile units to support many different bandclasses is increasing. Support for multiple bandclasses by mobile units and network components allows adaptation of communications traffic and bandclass resource allocation to facilitate load balancing in the system while minimizing call drops. In this regard, if a particular mobile device is only capable of communication on a single defined bandclass, the availability of services resources for that unit is limited by current usage of that particular bandclass in a given area, wherein services may be temporarily unavailable to the user if the supported bandclass is currently fully allocated.
Wireless communications systems and networks have been constructed and interconnected with wire-based telecommunications systems such as the pre-existing public switched telephone network (PSTN) to allow mobile devices to communicate with other mobile devices as well as with ordinary stationary telephones. Standardized protocols have been developed for messaging between various system components, such as the Telecommunications Industry Association/Electronic Industries Association (TIA/EIA) standardized intersystem operations protocol ANSI-TIA/EIA 41-D (IS-41), published by the American National Standards Institute (ANSI), and the GSM Mobile Application Part (MAP) protocol, a publication of the European Telecommunications Standards Institute (ETSI). Wireless systems include various infrastructure to service a wide geographic area divided into “cells” with base stations serving one or more such cells and networked mobile switching centers (MSCs) serving one or more base stations, where the MSCs are operatively coupled with one another and other systems by a wireless network and one or more MSCs may be coupled to a wire-based network to provide communications among and between wireless and/or wireline devices. To place a call, a user of a particular mobile communications unit interfaces with a base station serving the area in which the mobile unit is currently located, and the base station transmits the call to a corresponding MSC. The MSC, in turn, further routes the call as needed through the network and possibly to and/or through a wire-based system (PSTN) to connect the call with the proper destination. When an incoming call is placed to a mobile unit, for example, from a wireline telephone, the calling party initially dials the mobile unit number, and the call is routed through the PSTN, other networks, and/or wireless communications systems until the communication reaches the MSC serving the called party's mobile unit, which then connects the call to the mobile unit.
One important feature of mobile communications devices is the ability to send or receive communications regardless of the location of the mobile unit. Moreover, although a particular service provider or carrier provides wireless communications services to a given mobile unit, services are provided via other carriers when the user moves outside the areas specifically served by his or her service provider. In particular, if the new location of the mobile unit (a “visited” area) is serviced by a different carrier, the subscriber is said to be “roaming” out of the home service area. The various carriers have agreed to follow certain procedures in processing communications of each other's subscribers, wherein the service provider operating in the visited area validates roaming subscribers. When a mobile communications unit moves away from the associated home MSC, moreover, the serving or border MSC associated with the new location may need to know the bandclasses that the mobile unit is capable of supporting, in order to perform intelligent resource allocation and load balancing. Supported bandclass information is also desirable during visitor registration and/or updating of profile information for a registered visiting mobile unit.
Mobile devices typically do not convey bandclass information in an origination or page response message to a border or serving MSC. However, the receipt of one of these two messages at the serving or border MSC is an opportune time for that MSC to inform the mobile unit whether the unit's preferred bandclass could be used, or alternatively whether the mobile must use the bandclass on which it is currently accessing the system. In this regard, if the border MSC is currently unable to provide service on the current bandclass (the latest bandclass used by that mobile unit) and is unaware of the bandclasses supported by the mobile unit, the call may be dropped, even though the mobile supports another bandclass that is currently available. The current ANSI (IS-41) wireless protocol provides several messaging mechanisms by which border or serving MSCs may be provided with bandclass information. For instance, a serving MSC may send supported bandclass along with other information from an associated Visitor Location Register (VLR) record to a border MSC using an IS41 InterSystemPage (ISPAGE) or InterSystemPage2 (ISPAGE2) invoke message, and the border MSC then pages the mobile unit. As shown in the ANSI standards TIA-41-540-E and TIA-41-550-E, incorporated herein by reference, the ISPAGE and ISPAGE2 invoke messages can include an optional CDMABandClassList parameter that includes the bandclasses that the mobile supports. Having this information advantageously allows the border MSC to select one of the supported bandclasses for use by the mobile for a particular call based on current bandclass allocation in the area serviced by the border MSC. The CDMABandClassList parameter is also used for registering visiting mobiles in a serving MSC's area (e.g., in an IS-41 RegistrationNotification (REGNOT) return result message), as well as for updating profile information from the home to the visited MSC (using an IS-41 QualificationDirective (QUALDIR) invoke message).
However, REGNOT return result and the QUALDIR, ISPAGE, and ISPAGE2 invoke messages, and the CDMABandClassList parameter thereof, are relatively large, wherein transmission of these invoke messages occupies significant system resources. In particular, the CDMABandClassList parameter requires several octets (8 bits each) for each supported bandclass being reported in the above messages. Furthermore, as more and more bandclasses are to be supported, the CDMABandClassList parameter can potentially become huge if the mobile communications unit supports many different bandclasses. As discussed above, omitting the bandclass information from these messages inhibits the ability to perform load balancing, may lead to unnecessary call drops, and generally results in suboptimal system functionality. Accordingly, there remains a need for improved methods and systems for efficiently conveying bandclass information in wireless networks for purposes of delivering a terminating call or originating a call.